SpaceX Falcon 9 v1.1 - CASSIOPE - September, 2013 - GENERAL DISCUSSION THREAD

[edkyle99]

There is nothing to indicate that the second stage burn is a velocity reduction burn - note that this is specified for the first stage but *not* the second stage. It could just be simple restart to simulate GTO deployment.

With no payload on board, after having hauled a light payload to LEO, the second stage could be going further than a typical GTO.  I wonder how far.  EELV stages in this situation have either de-orbited or gone into solar orbit. 

 - Ed Kyle

[spacecowboy1]

Are there any viewing areas that offer a good line of sight view of launch pad SLC-4E? I am trying to decide between going to see the launch there or at SLC-6 tomorrow and there doesn't seem to be anywhere that offers a view of that pad.

[MP99]

Someone correct me if I'm wrong, but that's how I read the waiver.

No: that's why the waiver is needed.  The commonly present inversion would reduce launch availability so drastically that the 3e-5 E_c for overpressure is waived in favor of the total 1e-4 E_c for overpressure, toxics and debris, on the rationale that the specific E_cs for toxics and debris are low enough that the total E_c is less than 1e-4.

Thanks - useful info.

cheers, Martin

[c3infinity]

There is nothing to indicate that the second stage burn is a velocity reduction burn - note that this is specified for the first stage but *not* the second stage. It could just be simple restart to simulate GTO deployment.

With no payload on board, after having hauled a light payload to LEO, the second stage could be going further than a typical GTO.  I wonder how far.  EELV stages in this situation have either de-orbited or gone into solar orbit. 

 - Ed Kyle

My prediction would be earth escape, mostly because it doesn't leave the 2nd stage in orbit as debris. Additionally, with the light payload, my guess is there's plenty of propellant to attain a minimum c3. Any additional burn time simply adds energy to the orbit, which doesn't really matter.

The other option would be to aim for a GTO disposal apogee and let the burn time determine perigee and/or inclination. This would certainly be an interesting maneuver from the polar orbit the vehicle will be in.

I would be surprised if it re-entered, as burning to depletion would give a large area of possible debris impact. Though we will be able to rule out (or in) de-orbit of the 2nd stage when the NOTAMs come out.

[AJW]

From the DOT/FAA Waiver:  "The first stage will coast after stage separation, and then perform an experimental burn with three engines to reduce the entry velocity just prior to entry."

So will they simply reduce their forward velocity, or use this as an opportunity to test some aspect of boost-back as well?  The $64K question is where they plan to do the hover and the soft water landing.  They must also have a tug waiting.

[douglas100]

...So will they simply reduce their forward velocity, or use this as an opportunity to test some aspect of boost-back as well?  The $64K question is where they plan to do the hover and the soft water landing.  They must also have a tug waiting.

They have said they will not attempt fly back on this flight. Hovering and tugs have not been mentioned.

[DavidH]

...So will they simply reduce their forward velocity, or use this as an opportunity to test some aspect of boost-back as well?  The $64K question is where they plan to do the hover and the soft water landing.  They must also have a tug waiting.

They have said they will not attempt fly back on this flight. Hovering and tugs have not been mentioned.

Hovering was mentioned, by a different name, "impact the water with minimal velocity." Just loosen up your terminology for the poor guy.

The launch vehicle will also carry five secondary payloads to the
same orbit.  The first stage will coast after st age separation, and then perform an experimental burn with three engines to reduce the entry velocity just prior to entry.  Prior to landing in the water, it will perform a second experimental burn with one engine to impact the water with
minimal velocity.  The second stage will coast and then perform an experimental burn to depletion.

[aero]

If all goes well the first stage should float, shouldn't it?

[SpacexULA]

They have said they will not attempt fly back on this flight. Hovering and tugs have not been mentioned.

Would be a lot more cost effective to just use a water tight GPS and send a salvage company out to recover the stage from the ocean floor if/when the first stage is recovered.

2-3 weeks on the ocean floor is not going to do much more damage than a few hours floating would, especially considering the recovered stage's value for structural information and as a trophy would not be reduced much by the wait.

[SpacexULA]

If all goes well the first stage should float, shouldn't it?

Can't find the post now, but given known information it was speculated that the stage would float engine down with only a few meters of the stage outside the water.

[Lars_J]

If all goes well the first stage should float, shouldn't it?

Can't find the post now, but given known information it was speculated that the stage would float engine down with only a few meters of the stage outside the water.

If the tanks are intact and empty, most of it should be above water.

[cambrianera]

The stage (if intact) should float close to horizontal, barely touching the water with the interstage and dipping about half a meter on the engine side.

[Joffan]

Would be a lot more cost effective to just use a water tight GPS and send a salvage company out to recover the stage from the ocean floor if/when the first stage is recovered.

GPS doesn't work underwater. Perhaps you just meant a locator device (pinger).

2-3 weeks on the ocean floor is not going to do much more damage than a few hours floating would

Hitting the ocean floor might do some damage though, along with the pressure crushing the tanks. With a floating tank it might be feasible to add some protection to parts of interest within an hour.

[IRobot]

GPS doesn't work underwater. Perhaps you just meant a locator device (pinger).

$500 EPIRB collects GPS data and re transmits to a satellite. Not under water, but floating...

[aero]

The stage (if intact) should float close to horizontal, barely touching the water with the interstage and dipping about half a meter on the engine side.

Do you have numbers or is this speculation? If so, it seems pretty close to me. After all, the tanks will provide about 458 tonnes of buoyancy, and the empty stage only weighs about 28 tonnes. True, around 8 tonnes of that 28 tonnes is engine and thrust structure attached to the end of the 42.6 meter long stage, but that won't sink the stage, or even cause it to float upright, (I think). That's because the other 20 tonnes of stage 1 dry mass acts at the center of buoyancy. That should be enough data to calculate the attitude of the floating stage, but someone else can run the numbers, I hope.

[mr. mark]

I'll be looking for a good intial reduction burn and a controled flight down. The last second burn may not happen as planned on this first flight. Controling the first stage down seems to have been overlooked by some here. I think keeping the stage intact on the way down will be a challenge.

[Lurker Steve]

They have said they will not attempt fly back on this flight. Hovering and tugs have not been mentioned.

Would be a lot more cost effective to just use a water tight GPS and send a salvage company out to recover the stage from the ocean floor if/when the first stage is recovered.

2-3 weeks on the ocean floor is not going to do much more damage than a few hours floating would, especially considering the recovered stage's value for structural information and as a trophy would not be reduced much by the wait.

If the stage goes to the ocean floor, it's going to stay there. Recovery of items from the ocean floor isn't cheap.

[Robotbeat]

They have said they will not attempt fly back on this flight. Hovering and tugs have not been mentioned.

Would be a lot more cost effective to just use a water tight GPS and send a salvage company out to recover the stage from the ocean floor if/when the first stage is recovered.

2-3 weeks on the ocean floor is not going to do much more damage than a few hours floating would, especially considering the recovered stage's value for structural information and as a trophy would not be reduced much by the wait.

If the stage goes to the ocean floor, it's going to stay there. Recovery of items from the ocean floor isn't cheap.

Good point. Unless it's shallow (i.e. ~150ft or less).

[Antares]

If SpaceX doesn't have a tug out there, China might.  Hmmm, eyetar anyone?

[Prober]

From the DOT/FAA Waiver:  "The first stage will coast after stage separation, and then perform an experimental burn with three engines to reduce the entry velocity just prior to entry."

So will they simply reduce their forward velocity, or use this as an opportunity to test some aspect of boost-back as well?  The $64K question is where they plan to do the hover and the soft water landing.  They must also have a tug waiting.

the real question is if they have eyes in the sky to watch this event?